Due to its excellent biocompatibility, biostability and physical properties, polyurethane or polyurethane-containing polymers have been used to fabricate a large number of implantable devices, including pacemaker leads, artificial hearts, heart valves, stent coverings, artificial tendons, arteries and veins. See e.g., www.polymertech.com, wvvw.cardiotech-inc.com, and www.thermedicsinc.com. Also see Hsu et al., Soc. Biomaterials Trans., April 1998.
Known in the art is U.S. Pat. No. 3,975,350 which discloses the use of polyurethanes to make implants containing pharmaceutically active agents. This patent discloses that the active agents are mixed with the polyurethane polymer prior to being cast (or shaped) into a number of forms, including tubes, rods, films, etc.
Also known is U.S. Pat. No. 3,993,073 which discloses a delivery device for the controlled and continuous administration of a drug to a body site. The device disclosed therein comprises a reservoir containing a dissolved drug surrounded by a shaped wall which is insoluble in body fluid.
U.S. Pat. No. 3,948,254 discloses a drug delivery device for the administration of a drug. The drug is contained within a reservoir and the device comprises pores filled with a liquid which is permeable to the passage of the drug.
The inventors are not aware of any prior art polyurethane based drug delivery devices which can contain a drug in a solid form and which does not require a liquid medium or carrier for the diffusion of the drug at a zero order rate.